I have never in my life washed the outside of a cantaloupe and I have never in my life caught anything from them. Obviously this is now added to my list of things to do, but I consider myself fairly well up on kitchen hygiene and this is not something I have heard of before.
I didn’t used to wash the rind either but in past few years I have....and then, after cutting thru washed rind, I rinse the knife....before cutting up cantaloupe....paranoid, I guess.